Cooling system for homopolar machines



R. V. MORSE. COOLINQSYSIEM FOB HOMOPOLAR MACHINES.

N ILED'S .13. an. 1,327,350; Patented Jan. 6,1920.

2 ssssssss lager INMENTOR R. V. MORSE.-

COOLING SYSTEM FOR HOMOPOLAR MACHINES. APPLICATION FILED sen. 13. war.

- 1,327,350. P mted Jan. 6.1920

2 SHEETS-SHEET 2- plane UNITED STATES PATENT OFFICE.

ROBERT V. MORSE, OF ITHACA, NEW YORK.

COOLING SYSTEM FOR HOMOPOLAE MACHINES.

and. cooling of the armature and brushes,.

reduction of the size of the armature and current collecting apparatus, and the reduc tion of brush wear by the use of thorough cooling and moderate brush pressures; and other objects as will appanx- In the drawings, Figure -I is a longitudinal view partly in section, on the line I -I of Fig. II,-showing the ventilatin system apglied to a bipolar-homopolar inac ine. ig. II is a transverse cross-section on the ran plan III-411 of Fig. I, but on a slightl smaller scale, -showin the manner in whic l. the air blast is introduced byway of the field structure.- a

Fig. 1V illustrates another manner of introduciu the air blast.

Fig. z; is a longitudinal view, partly in section -sim ilnrto Fig. I,-but showing the cooling, system applied to a unipolar nuichine,-that is, a machine having but one homopolar field.

Fig. V] shows more in detail and on a larger scale the brushes and cooling apparatus.

Fig. VII is one View of a brush. 7

Fig. VIII shows one of the elements from. which a lmninutod brush may be built up.

Fig. IX shows iinother of the brush elements. which together with those of Fig. Vlil go to makc up a brush.

As shown in Fig. l and Fig); ll of the drawings. tlu- :u'nmturo l is nmunted on the shaft 2 and carries 'on or near its cylindrical surface armature conductor harsi'l, which extend in a general nx nl'dircctiou. 'lhcse eonductors fl are shown in Fig. 1 arranged in two belts in zones 3 and 3".--oach zone oncircling the armature in the region of n.

hmuopulur field, as will be dcscrihcd lalcr.

Specification of Letters Patent.

Homopolar Mil-- encircling the armature.

II-II of Fig. L-showing the arment of-brushes and cooling systena, i III is a transverse cross-section onthe added.

space.

in each ridge Patented Jan. 6, 1920.

Application filled September 13, 1917. Serial E0. 19 1368.

On each border of each armature bar acne is a belt of collector segments 4, 4', 4f, 4"',-, s milar in agpearance .to commutator segments, thoug the operation oi'the machine does not involve commutation. Each armature bar 3 connects ateach end with a collector figment 4, 'whereb the current is condiic to and from t armature ar. The iirmature bars 3 are insulated from each other and from the armature core,as are also the pollector segments 4. v

Surrounding the armature 1 and extending substantially the full len h thereof is the field structure 6, compo of a num r of axially extendin ridges which unite near the armature 1 to arm annular lefaces 8,

This eld structure 6 havingthe polefaoes 8 is excited by the coils!) to produce a magnetic flux as indicated by the dotted circles 'ofarrows in the upper part of Fig.1. ,The twofend' magnetic circuits combine with the centralma 'etic circuit so that one'broad homopolar eld is formed in the region of the zone 3' of the armature, and another broad homopolar field of opposite polaritgcpasses through the zone 3" ofthearmature'. The narrow homo olar fields at the ends of the armature are sliown as left of armature conductors, though of course theymay be utilized in cases where power 'ustifies the extra brush Thefields a are described are home'- lar because the magnetic circuit is similar of the old structure 6, so that an armature conductor 3 cuts a field of the same polarity at all points in its rotation; for example, the magnetic flux maybe considered inward at all points in, zone 3' and ontwu rd at all points in zone 3".

The brushes 10, 10', 10", 10', are arranged in sets or belts corresponding to the collector seginentsi, 4, 4", 4", as'shown in Fig. l, and each set of brushes encircles the armature as shown in F i II. Since there is no commutatioh of 'e armature current, the individual brushes of a set are placed close together as shown in Fig. II and Fig. VI. so as to form a practically continuous bclt around the armature. The narrow spaces between the successive brushes of :1 set are sufficient toprevent a short circuit through a collector segment 4. The brush sets lie in annular recesses or channels in the field structure, encircling the armature. The ridges of the field structure 6 bridge over these channels as shown at 11 in Fig. I and Fig. II, and the brushes 10, 10, etc. are accessible at points where the hollows between the ridges of the field structure open into the brush channels. Stationary conductors 12 connect the brushes from one side of an armature zone to the other,-the connections generally being arranged so as to put groups of armature bars 3 sncessively in series as the pass under the brushes in rotation, thus uildlng up the voltage of the machine to the desired-e tent. The operation of the electric circuit of the machine is described more in detail in the Patent No. 1,271,061, for dynamo-electric machine, granted to me July 2, 1918.

In homopolar machines it is highly desirable to keep the diameter of the armature as small as IS possible with the required power output; for though there is no electrical limitation to the R. 1'. M., the peripheral velocity has mechanical and practical limitations. While a high R. I. M. is desirable, particularly in turbine driven generators, it is also desirable to kt cp the peripheral velocity down, and therefore from both considerations it is hi hly important to have the diameter of tie armature as small as is feasible for a given power output. On the other hand, the power output at. a given speed depends largely on the amount of magnetic flux available in the homopolar fields; and since all the effective flux must pass through the core of thc armature 1 where saturation limits in practice the flux density in the iron, it is essential that every available square inch of the cross-section of the armature core be utilized for the magnetic flux-that is. that tlucoribe solid iron without the usual ventilating passages. It avails but little to widen the pole faces and lengthen the armature conductors in an etl'ort to increase the voltage: weaken lhr field. If the flux in the armature core lrmains the same, the voltage will he the same. sincr the number of lines of flux cut by the armature conductor is unchangrd so long as the amount of tlux through the armature core is unchan al. A little calculation will sliowthatthe width of an annular pole face need only equal one fourth the diameter of the armature core in order to have the same area and flux density; or where magnetic circuits are combined, the width of the annular pole face need only be equal to one half the armature diameter. llcnciit is the flux density in the core. rather than at the pole face, which is the controlling factor.

Thus it will be seen that it'is highly important to get as much magnetic flux as possible through the armature core. For this reason the l'OI'l should be solid. Without the usual air passages which offer a very poor path for the llux. In prior machines the result is merely to It is also important to 0001' the armature conductors 3 and the brushes 10,particularly the Iatter,-in order to permit good current densities and thus keep down the size of the current collecting apparatus,as well as to prevent excessive wear at the brushes and collector segments. The ventilating system about to be described does not choke the flux in the armgture core, and directs a blast of air over the armature conductors 8 and collector, segments 4 and around and through the brushes 10,the brushes having thin co per leaves which draw off and radiate the eat from the contact surfaces.

This ventilating'system consists of a fan or blower 14 preferably attached to the armature 1, though a separate blowermight be used. heading-from this blower-is an air duct 15 \vhichcnnducts the air to a slot 16, which extends through the annular pole face of an active armature zone 3' or 3". Referrin now to Fig. VI, it will be seen that'the s ot 16 passes through the pole face at a pointbetwecn the brushes 10, where the armature conductors 3 leave a brush for an instant as they pass on to the next brush. The ventilating slot 16 time does not inter, fcre with the efiectire field, nor unbalance the currents in the armature conductors that are carrying the load. Not only does the slot 16 not interfere withthe o aeration of the machine. but it-lmsitirelv air s the operation by having the trailing leaf of the brush he in a line with the slot 16 where the ficld is weakened. thus choking the current in each armature conductor 3 as it. is leaving the brush and preventing sparking at the brush tip. Sparking may he similarly reduced at brushcs where there is no ventilating slot 16 by cutting a slot 17 across the )ole face as shown in Fi VI.so as to wea on the field at the trailing end of the brush.

Each brush 10 is composedof anumber of thin copper leaves 18, extending from a solid back 19. (preferably laminated), which back has a flange 20 along one side in order that the brush may be clamped against the end of a stationary conductor 12 leading the current to or from the brush. The lcnyes, 18 a re separated frouicach other where they join the back 19. and may be slightly separated all the way out to their tips. One method of constructino such a brush is shown in Fig. V. Fig. VI I, and Fig. IX. Referring t ig- VIIL-Ql shows a copper stamping.

gap, an air duct conununicating with the air ap by way of the field structure and openmg into the air gap between the bordering belts of brushes, and means for forcing a current of air through the air duct into the air gap, and thence through the bordering I closely spaced cimumferentially and ar.

ranged in belts borderin and substantially inclosin the air gap, the rushes being composed 0 a large nmnber of flexible leaves secured together and spaced at their outer end but free to bend at their inner end where they contact with the collector segments, the space between leaves diminishing as they approach their inner contact ends so that the contact face of a brush is substant-iallr continuous, and means for blow ing air from the air gap. through the leaves of the brushes.

4; In a ventilating system for homopolar dynamo-electric machines, the combination of a field structure producing a homo lar field, a zone of armature conductors ying in said field and surrounded by an air gap, collector segments electrically connected with the armature conductors, brushes closely spaced circumferentially and arranged in belts bordering and substantially inclosing for homopola r the air gap, the brushes having curved. laminated backs and being composed of a large number of flexible leaves secured together and spaced at their outer end but free to bend at their inner end where they contact with the collector segments; the space between leaves diminishing as they approach their inner contact ends so that the contact face of a brush is substantially continuous, and means for blowing air from the air gap throuigh the leaves of the brushes.

5. n a homopolar dynamo-electric machine, the combination of a. homopolar field structure having an annular pole face, an armature having a zone of armature conductors adjacent the pole face but spaced therefrom to form an air gap therebetween, brushes closely spaced circumferentially around the armature and bordering and substantiallvinclosin the air gap, an air duct passing through t \e pole face in the region of the trailing tip of a brush so as to weaken the field where an armature conductor has its connection with a. brush interrupted, means forpmducing a similar efi'ect at the trailing ti of another brush, and means for forcin r a. urrent of air throu h the air duct into t 1e air gap, and from he air gap out through the brushes.

In witness whereof I have hereunto set my hand this 7th day of September, 1917.

ROBERT V. noRsF Witnesses;

Emmn' H. Wenznn J. S. 1, 

